1. Technical Field
The present invention relates in general to an improved hard disk drive and, in particular, to an improved system and apparatus for centering and attaching media disks to the hub of a spindle motor in a hard disk drive.
2. Description of the Related Art
Data access and storage systems typically comprise one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, one to six disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm).
A typical HDD also utilizes an actuator assembly. The actuator moves magnetic read/write heads to the desired location on the rotating disk so as to write information to or read data from that location. Within most HDDs, the magnetic read/write head is mounted on a slider. A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.
Typically, a slider is formed with an aerodynamic pattern of protrusions on its air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. A slider is associated with each side of each platter and flies just over the platter's surface. Each slider is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single movable unit having either a linear bearing or a rotary pivotal bearing system.
The head and arm assembly is linearly or pivotally moved utilizing a magnet/coil structure that is often called a voice coil motor (VCM). The stator of a VCM is mounted to a base plate or casting on which the spindle is also mounted. The base casting with its spindle, actuator VCM, and internal filtration system is then enclosed with a cover and seal assembly to ensure that no contaminants can enter and adversely affect the reliability of the slider flying over the disk. When current is fed to the motor, the VCM develops force or torque that is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. As the read/write head approaches a desired track, a reverse polarity signal is applied to the actuator, causing the signal to act as a brake, and ideally causing the read/write head to stop and settle directly over the desired track.
The attachment of the data storage disks to the hub of the spindle motor is typically accomplished via a disk clamp. The disk clamp retains the disks on the hub by attaching directly to the hub of the motor. It is very important to precisely center the disks to the hub in order to reduce installation-induced mass imbalance. Any imbalance in the disk pack and motor assembly is readily apparent when the assembly is rotated at operational speeds, which may range from 10,000 to 15,000 rpm. Thus, the reduction of imbalance prior to the balancing process can significantly improve the manufacturing process.
A conventional disk clamp 11 (FIG. 1) is typically centered on the spindle motor 13 by providing a rib 15 on top of the spindle motor hub 17. The rib 15 protrudes upward from the hub 17 and has an outer diameter 19 on which an inner diameter 21 of the disk clamp 11 is positioned and thereby centered. Moreover, very precise and expensive tooling is required to properly center and align the disk clamp 11 and hub 17. Although this design is workable, an improved system and apparatus for attaching and centering a disk clamp on the hub of a spindle motor in a hard disk drive would be desirable.